Photos: World's Hidden Man-made Wonders

A tree grows from a structure at Sambor Prei Kuk, which has 52 ancient temples spread across a nearly three-square-mile swath of jungle in Cambodia's Kampong Thom province.

(Baldiri/Wikimedia Commons)

Incan ruins on the hilltop of Choquequirao in Peru.

(Martin St-Amant/Wikimedia Commons)

Gateway to the entrance of Bara Imambara, a palace complex containing an elaborate maze in Lucknow, India.

(Sayed Mohammad Faiz Haider Rizvi/Wikimedia Commons)

The Indian palace complex Bara Imambara seen from one of its many corridors.

(Sayed Mohammad Faiz Haider Rizvi/Wikimedia Commons)

A view of the roof of Bara Imambara in Lucknow, India.

(Sayed Mohammad Faiz Haider Rizvi/Wikimedia Commons)

Cambodia's little-known hidden temple complex of Sambor Prei Kuk, whose structures were built during the 7th century and predate those at Angkor Wat by some 600 years.

(Baldiri/Wikimedia Commons)

Kizhi Island in northern Russia is an open-air museum with a cluster of churches at its southern tip. Aspen wood was used in the construction of the buildings, including the shingles of the 22 domes of the Church of the Transfiguration of Our Savior.

The Church of the Transfiguration of Our Savior on Kizhi Island, Russia.

(Olivier Martel/Corbis)

An up-close look at the intricate top of the Church of Transfiguration of Our Savior in Kizhi.

(Gérard Janot/Wikimedia Commons)

Naqsh-e Jahan Square in Isfahan, Iran, is bounded by four monumental structures: the mosaic-tiled Royal Mosque to the south, the Portico of Qaysariyyeh to the north, the Mosque of Sheykh Lotfollah to the east, and the magnificent entrance to Ali Qapu palace and the royal gardens to the west.

(Nick Taylor/Wikimedia Commons)

Exquisite details of a music room at Ali Qapu palace in Isfahan, Iran.

(Kiumars/Wikimedia Commons)

Naqsh-e Jahan Square from Ali Qapu palace in Isfahan.

(Arad/Wikimedia Commons)

The belowground church of St. George in Lalibela, Ethiopia.

(Julien Demade/Wikimedia Commons)

A closer view of St. George church in Lalibela.

(Giustino Taken/Wikimedia Commons)

A 15th-century wall at Choquequirao, whose nearly 200 slope terraces were built about 6,000 feet above the glacier-fed Apurímac River.

(Courtesy Gihan Tubbeh/PromPeru)

It took 90 years to carve the 233-foot-tall Leshan Giant Buddha out of a remote Chinese mountainside in the 8th century.

(Ariel Steiner/Wikimedia Commons)

The head of the Giant Buddha in Leshan, China, is covered with 1,021 intricate, twisted hair buns hiding a complex drainage system that helps preserve the statue.

(Kounosu/Wikimedia Commons)

The little-known Mirador Basin, hidden among 2,000 years of jungle growth in northern Guatemala, consists of five Preclassic Mayan cities, each larger and older than the nearby (and far more famous) Tikal by 1,000 years.

Structures at the Preclassic Mayan city of El Mirador. An international effort led by the Global Heritage Fund with help from the Guatemalan and U.S. governments is underway to establish an 810,000-acre national park in the region.

(Juan José Acevedo Góngora/Wikimedia Commons)

An aerial view of the megalithic temple of Mnajdra in Malta.

(Pasquale Sorrentino/AGE)

The interior of a megalithic temple on Malta.

(Courtesy Malta Tourism Authority)

Mnajdra is one of a series of stone temples on the islands of Malta and Gozo that are considered to be the world's oldest freestanding monuments.